Vehicular cooling system using air conditioner refrigerant

ABSTRACT

A cooling system for a vehicle which includes a coolant circuit ( 21 ) for circulating coolant to cool a unit ( 1 ) carried on the vehicle; a refrigerant circuit ( 41 ) for circulating refrigerant for an air conditioner of the vehicle; and a heat exchanger ( 15 ) connected to the coolant and refrigerant circuits ( 21, 41 ), provided with a storage medium ( 25 ) for storing cool of the refrigerant. The heat exchanger ( 15 ) carries out heat-exchanges between the coolant and the storage medium, and between the coolant and the refrigerant.

TECHNICAL FIELD

The present invention relates to a vehicular cooling system to cool aunit carried on a vehicle, particularly to a vehicular cooling systemusing air conditioner refrigerant as heat sink.

BACKGROUND ART

Japanese Utility Model Application Laid-Open No. 4-116660 discloses afuel cooling system using air conditioner refrigerant to suppress fueltemperature rise.

Japanese Patent Application Laid-Open No. 11-337193 discloses a coolingsystem for a motor or an inverter using air conditioner refrigerant.

DISCLOSURE OF INVENTION

Power generating unit of a vehicle, such as an internal combustionengine (ICE), is efficiently cooled by coolant, temperature of which issufficiently higher than outside air temperature. Refrigerant has neverbeen used for cooling the unit.

Fuel cell is also cooled by coolant, and is not suitable for a directcooling by refrigerant. For some fuel cells, refrigerant lines cannot beinstalled inside.

A radiator is employed, in the same manner as that of an ICE poweredvehicle, to remove heat in the coolant of the fuel cell. Requiredcooling capacity of the radiator during high power operation isapproximately equal to that of the ICE radiator. For a stable operation,the coolant of the fuel cell is required to be kept lower in temperaturethan that of the ICE. Because of the smaller temperature differencebetween the coolant and the outside air, the radiator for the fuel cellneeds to have larger contact area with the outside air than the ICEradiator to secure the required cooling capacity, resulting in a size ofthe radiator exceeding allowable limit for mounting on the vehicle,otherwise output power of the vehicle is sacrificed to keep down heatgeneration.

An object of the present invention is to provide a vehicular coolingsystem for a unit carried on a vehicle, with enhanced cooling capacity.

An aspect of the present invention is a cooling system for a vehiclecomprising: a coolant circuit for circulating coolant to cool a unitcarried on the vehicle; a refrigerant circuit for circulatingrefrigerant for an air conditioner of the vehicle; and a heat exchangerconnected to the coolant and refrigerant circuits, provided with astorage medium for storing cool of the refrigerant, the heat exchangercarrying out heat-exchanges between the coolant and the storage medium,and between the coolant and the refrigerant.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention will now be described with reference to the accompanyingdrawings wherein:

FIG. 1 is a schematic diagram showing an entire configuration of avehicular cooling system according to a first embodiment of the presentinvention.

FIG. 2 is a schematic diagram showing a heat exchanger, and a flow ofrefrigerant and coolant in the vehicular cooling system of FIG. 1.

FIG. 3 is a flowchart showing an operation of the vehicular coolingsystem of FIG. 1.

FIG. 4 is a graph of cooling water temperature explaining an increaserate of the cooling water temperature.

FIG. 5 is a graph of an average fuel cell output per unit timeexplaining an increase rate of the average fuel cell output.

FIG. 6 is a schematic diagram showing a heat exchanger, and a flow ofrefrigerant and coolant in a vehicular cooling system according to asecond embodiment of the present invention.

FIG. 7 is a flowchart showing an operation of the vehicular coolingsystem of FIG. 6.

BEST MODE FOR CARRYING OUT THE INVENTION

Embodiments of the present invention will be explained below withreference to the drawings, wherein like members are designated by likereference characters.

As shown in FIG. 1, a fuel cell 1 as a unit carried on a vehicle isconnected to a radiator 3 by lines 5 and 7. The line 5 has a water pump9 installed therein, and cooling water as coolant discharged therefromflows to the radiator 3. The line 7 has a coolant line switching valve11 installed therein, which is connected to a lower side in the drawingof a heat exchanger 15 by a line 13. The line 7 between the coolant lineswitching valve 11 and the fuel cell 1 is connected to an upper side inthe drawing of the heat exchanger 15 by a line 17.

The lines 13 and 17 constitute a coolant bypass 19. The lines 5 and 7,and the coolant bypass 19 constitute a coolant circuit 21 of a coolingsystem for the fuel cell 1. By operating the coolant line switchingvalve 11, cooling water discharged from the radiator 3 is switchedbetween a state of flowing through the coolant bypass 19 and the heatexchanger 15 to the fuel cell 1, and a state of flowing not through thecoolant bypass 19 but directly from the coolant line switching valve 11to the fuel cell 1. This enables controlling a temperature of thecooling water in dependence to a temperature situation of the fuel cell1, whereby the temperature of the cooling water is stabilized.

As shown in FIG. 2, the heat exchanger 15 includes a coolant region 23,to which the lines 13 and 17 are connected. A storage medium 25 isarranged on the left side of the coolant region 23 in the drawing and,on its right side, a first refrigerant region 27 is arranged, whichrefrigerant used for a vehicular air conditioner as a heat sink,described later, flows into. A second refrigerant region 29 is arrangedon a side of the storage medium 25 opposite the coolant region 23. Atthe heat exchanger 15, heat-exchanges can be carried out between thecooling water of the coolant region 23 and the refrigerant of the firstrefrigerant region 27, between the refrigerant of the second refrigerantregion 29 and the storage medium 25, and between the cooling water ofthe coolant region 23 and the storage medium 25. Accordingly, thecooling water of the fuel cell 1 can be efficiently cooled by therefrigerant for the air conditioner, and the storage medium 25 whichstores cool of the refrigerant, whereby cooling capacity of the coolingsystem for the fuel cell 1 is enhanced.

As shown in FIG. 1, the vehicular air conditioner, i.e., an airconditioner unit installed in the vehicle, includes an electriccompressor 31, a condenser 33 for condensing a flown-in refrigerantdischarged from the electric compressor 31, a liquid tank 35, and anevaporator 39 in a duct 37 connected with the inside of a car room toevaporate liquid refrigerant, which are all connected constituting arefrigerant circuit 41. The electric compressor 31 is controlled by anelectric compressor inverter 43.

A line 45 between the evaporator 39 and the liquid tank 35 has arefrigerant line switching valve 47 installed therein. This refrigerantline switching valve 47 is connected to an upper side in the drawing ofthe first refrigerant region 27 of the heat exchanger 15 by a line 51,and to an upper side in the drawing of the second refrigerant region 29of the heat exchanger 15 by a line 53. Lower sides in the drawing of thefirst and second refrigerant regions 27 and 29 are connected to eachother by a line 55. The line 55 and a line 57 between the electriccompressor 31 and the evaporator 39 are connected to each other by aline 59. The lines 51, 53, 55 and 59 constitute a refrigerant bypass 61.By operating the refrigerant line switching valve 47, refrigerant fromthe liquid tank 35 is switched to a state of flowing to the evaporator39 through a line 45 a, a state of flowing to the line 51, a state offlowing to both of the lines 45 a and 51, or a state of flowing to bothof the lines 45 a and 53. Flow of the refrigerant into the refrigerantbypass 61 is controlled in dependence to the temperature situation ofthe fuel cell 1 or a running condition of the air conditioner. Thetemperature of the cooling water is lowered with minimized influences onair conditioner performance.

In the line 7 before the fuel cell 1, a water temperature sensor 63 isprovided for detecting a cooling water temperature, and the storagemedium 25 is provided with a temperature sensor 64 for detecting itstemperature. A detection value of each of the water temperature sensors63 and 64 is sent to a vehicular control unit (VCU) 65 as a controlunit. Receiving an output value from the fuel cell 1 and the detectionvalues from the water temperature sensors 63 and 64, the VCU 65 outputsoperation signals to the coolant line switching valve 11 and therefrigerant line switching valve 47.

The electric compressor inverter 43 receives an operation signal from anair conditioner control unit (ACCU) 67 to control the electriccompressor 31. A detection value of an atmosphere temperature sensor 69downstream the evaporator 39 is sent to the ACCU 67.

Next, an operation of the foregoing vehicular cooling system will bedescribed based on a flowchart shown in FIG. 3. When an ignition switch(IGN) of the vehicle is turned ON, the coolant line switching valve 11is switched so that the coolant can directly flow from the coolant lineswitching valve 11 to the line 7 without flowing through the coolantbypass 19. The refrigerant line switching valve 47 is switched so thatthe refrigerant can directly flow from the refrigerant line switchingvalve 47 to the evaporator 39 through the line 45 a without flowingthrough the refrigerant bypass 61 (step 301).

In this state, the VCU 65 takes in a cooling water temperature Twdetected by the water temperature sensor 63 to compare the temperatureTw with a predetermined value Tmax, and decides whether Tw≧Tmax isestablished or not (step 303). Herein, if Tw≧Tmax, which means a highdriving load of the fuel cell 1 with insufficient heat removal at theradiator 3 causing the cooling water temperature to rise, isestablished, heat-exchange between the cooling water and the refrigerantis carried out at the heat exchanger 15 to lower the cooling watertemperature. The predetermined value Tmax is set, for example, lowerthan a temperature of the fuel cell 1 at maximum load operation.

At this time, the coolant line switching valve 11 is switched to a statewhere the cooling water flows through the coolant bypass 19 (line 13).The refrigerant line switching valve 47 is switched to a state where therefrigerant flows through the line 51 to the first refrigerant region27. The ACCU 67 outputs a signal to the electric compressor inverter 43so as to maximize a cooling power and an amount of heat exchangedbetween the coolant and the refrigerant at the heat exchanger 15 (step305).

By the switching of each of the line switching valves 11 and 47, thecooling water flows from the line 13 to the coolant region 23 of theheat exchanger 15, then flows to the line 17 and returns to the line 7.The refrigerant flows from the line 51 to the first refrigerant region27, then flows to the lines 55 and 59, and returns to the line 57. Then,the refrigerant is sucked into the electric compressor 31. Accordingly,at the heat exchanger 15, the cooling water in the coolant region 23absorbs cool from the refrigerant in the first refrigerant region 27. Atthis time, the fuel cell 1 is sufficiently cooled by the cooling watereffectively cooled by the refrigerant of the maximized cooling power.

If the cooling water temperature Tw is lower than the predeterminedvalue Tmax, the cooling water temperature Tw is compared with a secondpredetermined value T1 lower than the predetermined value Tmax, anddecision is made as to whether the cooling water temperature Tw is lowerthan the predetermined value Tmax and equal to or higher than the secondpredetermined value T1, i.e., Tmax>Tw≧T1 is established or not (step307). Herein, if Tmax>Tw≧T1 is established, the VCU 65 calculates awater temperature increase rate of the cooling water Tp=ΔTw(° C.)/ΔS(s),and an increase rate of an average output of the fuel cell 1 per unittime Pp=ΔPwave(kW)/ΔS(s), respectively by a temperature increase ratecalculating unit and an output increase rate calculating unit, anddecides whether the increase rates Tp and Pp are respectively equal toor higher than set values α and β (steps 309 and 311).

In this case, as shown in FIG. 4, with an abscissa axis indicating time[sec.], and an ordinate axis a cooling water temperature [° C.], thewater temperature increase rate Tp is represented by{Tw(n)-Tw(n-1)}/{S(n)-S(n-1)}. As shown in FIG. 5, with an abscissa axisindicating time [sec.], and an ordinate axis the average output [kW],the average output increase rate Pp is represented by{Pwave(n)-Pwave(n-1)}/{S(n)-S(n-1)}. In FIG. 5, a polygonal line Parepresents a real output of the fuel cell 1, and a curve Pb an averagevalue of real outputs per unit time.

In the case the output of the fuel cell 1 as well as the temperature ofthe cooling water fluctuates a lot, if the increase rates Tp and Pp aredetermined to be respectively equal to or higher than the predeterminedvalues α and β, the coolant line switching valve 11 is switched to astate where the cooling water flows through the coolant bypass 19 (line13) (step 313). At this time, the refrigerant line switching valve 47 ismaintained in the initial state where the refrigerant flows only to theair conditioner line 45 a without flowing through the refrigerant bypass61.

Thus, the cooling water flows into the coolant region 23 of the heatexchanger 15, and the cooling water in this coolant region 23 is cooledby heat-exchange with the storage medium 25 containing the cool storedbeforehand from the refrigerant. Operation of storing cool in thestorage medium 25 is carried out by switching the refrigerant lineswitching valve 47 so that the refrigerant flows through the line 53 toreach the second refrigerant region 29 to carry out heat-exchange withthe storage medium 25.

As described above, when the output of the fuel cell 1 fluctuates a lotand so does the temperature of the cooling water accordingly, theheat-exchange with the storage medium 25 stabilizes the cooling watertemperature and suppresses the change thereof.

Then, decision is made as to whether a temperature of the storage mediumTs detected by the temperature sensor 64 is equal to or higher than amelting point of the storage medium Tsmelt as a stipulated value, i.e.,Ts≧Tsmelt is established or not (step 315). Herein, if Ts≧Tsmelt isestablished, the ACCU 67 decides whether a cool-down signal is ON ornot, the cool-down signal being ON when a car room temperature is higherby a given range compared to a set temperature of the air conditioner(step 317).

In this case, if the cool-down signal is OFF and if the car roomtemperature is low, the refrigerant line switching valve 47 is switchedto a state where the refrigerant flows to the line 51 and to theevaporator 39 through the line 45 a (step 319). Accordingly, therefrigerant flowing through the line 51 into the first refrigerantregion 27 is subjected to beat-exchange with the cooling water in thecoolant region 23 in place of the storage medium 25, which has reachedthe melting point Tsmelt or more, and the cooling water is continuouslycooled.

Also at this time, by increasing a cooling power according to demand(step 319), it is possible to increase the amount of heat exchangedbetween the cooling water and the refrigerant without affecting airconditioning performance.

Then, decision is made as to whether the cooling water temperature Twhas dropped below the second predetermined value T1, i.e., Tw<T1 isestablished or not (step 321). Herein, if Tw<T1 is established, it isnot necessary to cool the cooling water. Thus, the process returns tothe step 301, where the cooling of the cooling water by the refrigerantis stopped.

If the cool-down signal is ON in the step 317, since it is necessary toplace priority on cooling of the inside of the car room, the processreturns to the step 301, where the cooling of the cooling water by therefrigerant is stopped.

The flowing of the cooling water into the coolant bypass 19 iscontrolled in dependence to the above-described increase rates Tp and Ppof the cooling water temperature Tw and the average output Pwave. Thus,the temperature of the cooling water is accurately and quicklycontrolled in dependence to the state of the fuel cell 1 to bestabilized more, whereby an operation of the cooling system is limitedto the minimum necessary. In this case, an amount of fluctuation in thecooling water temperature Tw is reduced, and the temperature changes ofthe fuel cell 1 are suppressed, thus enhancing the performance of thefuel cell 1.

If in the step 307, Tmax>Tw≧T1 is not established and the coolingtemperature Tw is lower than the second predetermined value T1, decisionis made as to whether the temperature Ts of the storage medium 25detected by the temperature sensor 64 is equal to or higher than themelting point Tsmelt as the stipulated value or not (step 323). Herein,if Ts≧Tsmelt is established, decision is made as to whether thecool-down signal is ON or not (step 325). If the cool-down signal isOFF, and if the temperature in the car room is low, the refrigerant lineswitching valve 47 is switched to a state where the refrigerant flows tothe line 53 and to the evaporator 39 through the line 45 a (step 327).Accordingly, the refrigerant flowing through the line 53 into the secondrefrigerant region 29 exchanges heat with the storage medium 25, andcool is stored in the storage medium 25, which has reached the meltingpoint Tsmelt or more.

If the temperature Ts of the storage medium 25 is lower than Tsmelt inthe step 323, and if the cool-down signal is ON in the step 325, theoperation of storing cool in the storage medium 25 is made unnecessary,while cooling is necessary in the car room. Therefore, the processreturns to the step 301, where the coolant and refrigerant lineswitching valves 11 and 47 are both returned to the initial states.

Thus, it is possible to store the cool for cooling the cooling water inthe storage medium 25 without affecting the air conditioningperformance.

Then, decision is made as to whether the cooling water temperature Tw isequal to or higher than the above-described second predetermined valueT1 or not (step 329). Herein, if Tw≧T1 is established and if the coolingwater temperature is increased, the process returns to the step 301.Conversely, if the cooling water temperature Tw is lower than the secondpredetermined value T1, the process returns to the step 323, and theoperations thereafter are repeated.

According to a second embodiment of the present invention shown in FIG.6, a heat exchanger 71 includes a refrigerant region 73, through whichrefrigerant passes. A storage medium 75 is arranged on the left side inthe drawing of the coolant region 73 and, on its right side, a firstcoolant region 77 is arranged, into which cooling water flows. A secondcoolant region 79 is arranged on a side of the storage medium 75opposite the coolant region 73. Specifically, at the heat exchanger 71,heat can be exchanged between the cooling water of the first coolantregion 77 and the refrigerant of the refrigerant region 73, between therefrigerant of the refrigerant region 73 and the storage medium 75, andbetween the cooling water of the coolant region 79 and the storagemedium 75.

A refrigerant line switching valve 81 installed in the refrigerantcircuit 41 is connected to an upper side in the drawing of therefrigerant region 73 by a line 83, and a lower side in the drawing ofthe refrigerant region 73 is connected to the line 57 between theelectric compressor 31 and the evaporator 39 of FIG. 1 by a line 85. Thelines 83 and 85 constitute a refrigerant bypass 87. A switchingoperation of the refrigerant line switching valve 81 enables refrigerantflowing in from the liquid tank 35 to be switched between a state offlowing to the evaporator 39 through the line 45 a and a state offlowing to the line 83, or even to a state of flowing to both.

A coolant line switching valve 89 installed in the line 7 is connectedto lower sides in the drawing of the first and second coolant regions 77and 79 respectively by lines 91 and 93. Lines 95 and 97 are respectivelyconnected to uppers sides in the drawing of the first and second coolantregions 77 and 79. These lines 95 and 97 are connected through a line 99to the line 7. The lines 91, 93, 95, 97 and 99 constitute a coolantbypass 101, and the coolant bypass 101 and the lines 5 and 7 constitutethe coolant circuit 21.

Specifically, in the example of FIG. 2, the refrigerant bypass line hastwo lines 51 and 53, and the coolant bypass line has one line 13. Withsuch a structure, switching is executed by the refrigerant lineswitching valve 47 between the cooling of the cooling water by therefrigerant and that by the storage medium 25. On the other band, in theexample of FIG. 6, the refrigerant bypass line has one line 83, thecoolant bypass line has two lines 91 and 93. Switching is executed bythe coolant line switching valve 89 between cooling of the cooling waterby the refrigerant and that by the storage medium 75.

FIG. 7 is a flowchart showing an operation of the vehicular coolingsystem of FIG. 6. Herein, only operation process different from those ofthe flowchart of FIG. 3 are described.

When the cooling water temperature Tw is equal to or higher than Tmax(step 303), the coolant line switching valve 89 is switched to a statewhere the cooling water flows through the line 91 into the first coolantregion 71. The refrigerant line switching valve 81 is switched to astate where the refrigerant flows through the line 83 into therefrigerant region 73, cooling power is maximized by the ACCU 67, and anamount of heat exchanged between the cooling water and the refrigerantis maximized at the heat exchanger 71 (step 701). Accordingly, in astate of a high cooling water temperature, priority is placed onlowering of the cooling water temperature, and the cooling water iseffectively cooled.

If the cooling water temperature Tw is lower than Tmax and equal to orhigher than T1 (step 307), and if the increase rate Tp of the coolingwater temperature and the increase rate Pp of the average output arerespectively equal to or higher than set values α and β (steps 309 and311), the coolant line switching valve 89 is switched to a state wherethe cooling water flows through the line 93 (step 703). The refrigerantline switching valve 81 is maintained in an initial state where therefrigerant only flows to the air conditioner line 45 a without flowingthrough the refrigerant bypass 87.

Thus, the cooling water flows into the second coolant region 79 of theheat exchanger 71, and the cooling water in this second coolant region79 is cooled by the storage medium 75 containing the cool storedbeforehand from the refrigerant.

Further, when a temperature Ts of the storage medium 75 is equal to orhigher than a melting point Tsmelt (step 315), and when a cool-downsignal is OFF (step 317), the refrigerant line switching valve 81 isswitched to a state where the refrigerant flows to the line 83 and tothe evaporator 39 through the line 45 a (step 705). Accordingly, therefrigerant flowing through the line 83 into the refrigerant region 73is subjected to heat-exchange with the cooling water in the secondcoolant region 79 through the storage medium 75 which has reached themelting point Tsmelt or more, and the cooling water is continuouslycooled.

Also at this time, by increasing the cooling power according to demand(step 709), it is possible to increase the amount of the heat exchangedbetween the cooling water and the refrigerant without affecting airconditioning performance.

If the cooling temperature drops below T1 (step 307), and if thetemperature Ts of the storage medium 75 is equal to or higher than themelting point Tsmelt (step 323) and the cool-down signal is OFF (step325), the refrigerant line switching valve 81 is switched to a statewhere the refrigerant flows to the line 83, and the line 45 a to theevaporator 39 (step 707). Accordingly, the refrigerant flowing throughthe line 83 into the refrigerant region 73 exchanges heat with thestorage medium 75, and cool is stored in the storage medium 75, whichhas reached the melting point Tsmelt or more.

The present disclosure relates to subject matter contained in JapanesePatent Application No. 2001-332728, filed on Oct. 30, 2001, thedisclosure of which is expressly incorporated herein by reference in itsentirety.

The invention may be practiced or embodied in still other ways withoutdeparting from the spirit or essential character thereof. The fuel cellwas used as the unit carried on the vehicle in each of the foregoingembodiments, however, as long as a temperature of coolant is about 80°C., the unit may be a driving motor.

The preferred embodiment described herein is therefore illustrative andnot restrictive, the scope of the invention being indicated by theclaims and all variations which come within the meaning of claims areintended to be embraced therein.

INDUSTRIAL APPLICABILITY

As described above, according to the vehicular cooling system of thepresent invention, the coolant for cooling the unit carried on thevehicle exchanges heat with the air conditioner refrigerant and thestorage medium in which the cool of the refrigerant is stored, at theheat exchanger connected to the coolant and refrigerant circuits. Thus,the coolant is sufficiently and stably cooled, thereby improving thecooling capacity of the system.

Furthermore, the line switching valves respectively provided in thecoolant and refrigerant circuits are controlled to make optimumcombinations of the heat-exchange between the refrigerant and thecoolant, between the coolant and the storage medium, and between thestorage medium and the refrigerant. Thus, the cooling of the unit can becarried out, flexibly and quickly dealing with changes in the coolanttemperature, the coolant temperature increase rate, the unit outputincrease rate, the temperature of the storage medium, the temperature inthe car room, and the like. Therefore, the system is useful as avehicular cooling system.

1. A cooling system for a vehicle comprising: a coolant circuit forcirculating coolant to cool a unit carried on the vehicle; a refrigerantcircuit for circulating refrigerant for an air conditioner of thevehicle; and a heat exchanger connected to the coolant and refrigerantcircuits, provided with a storage medium for storing cool of therefrigerant, the heat exchanger carrying out heat-exchanges between thecoolant and the storage medium, and between the coolant and therefrigerant.
 2. The cooling system for a vehicle according to claim 1,further comprising: a coolant bypass provided in the coolant circuit,connected to the heat exchanger; and a coolant line switching valve forswitching flow of the coolant into the coolant bypass on and off.
 3. Acooling system for a vehicle according to claim 1, further comprising: arefrigerant bypass provided in the refrigerant circuit, connected to theheat exchanger; and a refrigerant line switching valve for switchingflow of the refrigerant into the refrigerant bypass on and off.
 4. Acooling system for a vehicle according to claim 3, wherein therefrigerant line switching valve can be switched to allow therefrigerant to flow to either the heat exchanger or an evaporator of theair conditioner, or both of the heat exchanger and the evaporator.
 5. Acooling system for a vehicle according to claim 1, wherein the unit is afuel cell.
 6. A vehicle, comprising: a cooling system according to claim5.
 7. A vehicle, comprising: a cooling system according to claim
 1. 8. Acooling system for a vehicle comprising: a coolant circuit forcirculating coolant to cool a unit carried on the vehicle; arefrigerator circuit for circulating refrigerant for an air conditionerof the vehicle; and a heat exchanger connected to the coolant andrefrigerant circuits, provided with a storage medium for storing cool ofthe refrigerant, the heat exchanger carrying out heat-exchanges betweenthe coolant and the storage medium, and between the coolant and therefrigerant; wherein the heat exchanger includes: a coolant regionarranged on one side of the storage medium, connected to the coolantcircuit; a first refrigerant region arranged on a side of the coolantregion opposite the storage medium, connected to the refrigerantcircuit; and a second refrigerant region arranged on the other side ofthe storage medium, connected to the refrigerant circuit, and whereinthe heat exchanger carries out heat-exchanges between the coolant andthe storage medium, between the coolant and the refrigerant, and betweenthe storage medium and the refrigerant.
 9. A cooling system for avehicle according to claim 8, wherein the unit is a fuel cell.
 10. Acooling system for a vehicle comprising: a coolant circuit forcirculating coolant to cool a unit carried on the vehicle; arefrigerator circuit for circulating refrigerant for an air conditionerof the vehicle; and a heat exchanger connected to the coolant andrefrigerant circuits, provided with a storage medium for storing cool ofthe refrigerant, the heat exchanger carrying out heat-exchanges betweenthe coolant and the storage medium, and between the coolant and therefrigerant; wherein the heat exchanger includes: a refrigerant regionon one side of the storage medium, connected to the refrigerant circuit;a first coolant region arranged on a side of the refrigerant regionopposite the storage medium, connected to the coolant circuit; and asecond coolant region arranged on the other side of the storage medium,connected to the coolant circuit wherein the heat exchanger carries outheat-exchanges between the refrigerant and the storage medium, betweenthe refrigerant and the coolant, and between the storage medium and thecoolant.
 11. A cooling system for a vehicle according to claim 10,wherein the unit is a fuel cell.
 12. A cooling system for a vehiclecomprising: a coolant circuit for circulating coolant to cool a unitcarried on the vehicle; a refrigerator circuit for circulatingrefrigerant for an air conditioner of the vehicle; a heat exchangerconnected to the coolant and refrigerant circuits, provided with astorage medium for storing cool of the refrigerant, the heat exchangercarrying out heat-exchanges between the coolant and the storage medium,and between the coolant and the refrigerant; a coolant bypass providedin the coolant circuit, connected to the heat exchanger; a coolant lineswitching valve for switching flow of the coolant into the coolantbypass on and off; a temperature increase rate calculating unit forcalculating an increase rate of a temperature of the coolant; a outputincrease rate calculating unit for calculating an increase rate of anoutput of the unit; and a control unit for controlling switching of thecoolant line switching valve in dependence to the calculated coolanttemperature and unit output increase rates.
 13. A cooling system for avehicle according to claim 12, wherein the coolant line switching valveis controlled to turn on the flow of the coolant into the coolant bypassto carry out heat-exchange between the coolant and the storage medium,as the calculated coolant temperature and unit output increase rates arerespectively equal to or higher than respective set values.
 14. Acooling system for a vehicle according to claim 12, wherein the unit isa fuel cell.
 15. A cooling system for a vehicle comprising: a coolantcircuit for circulating coolant to cool a unit carried on the vehicle; arefrigerant circuit for circulating refrigerant for an air conditionerof the vehicle; a heat exchanger connected to the coolant andrefrigerant circuits, provided with a storage medium for storing cool ofthe refrigerant, the heat exchanger carrying out heat-exchanges betweenthe coolant and the storage medium, and between the coolant and therefrigerant; a coolant bypass provided in the coolant circuit, connectedto the heat exchanger; a coolant line switching valve for switching flowof the coolant into the coolant bypass on and off; a refrigerant bypassprovided in the refrigerant circuit, connected to the heat exchanger; arefrigerant line switching valve for switching flow of the refrigerantinto the refrigerant bypass on and off; and a control unit forcontrolling the coolant line switching valve to allow the coolant toflow into the coolant bypass and the refrigerant line switching valve toallow the refrigerant to flow into the refrigerant bypass, as coolanttemperature is equal to or higher than a first predetermined value. 16.A cooling system for a vehicle according to claim 15, wherein thecoolant line switching valve is controlled in dependence to increaserates of the coolant temperature and an output of the unit, and therefrigerant line switching valve is controlled in dependence to atemperature of the storage medium, as the coolant temperature is lowerthan the first predetermined value and equal to or higher than a secondpredetermined value.
 17. A cooling system for a vehicle according toclaim 16, wherein the coolant and refrigerant line switching valves arecontrolled to carry out heat-exchange between the storage medium and therefrigerant, as the temperature of the coolant is lower than the secondpredetermined value, the temperature of the storage medium is equal toor higher than a stipulated value, and a temperature in a car room ishigher than a setting temperature by a predetermined range.
 18. Acooling system for a vehicle according to claim 17, wherein a compressorof the air conditioner comprises an electric compressor for variablecooling power, and the cooling power is increased, as heat-exchangebetween the storage medium and the refrigerant is carried out to storethe cool of the refrigerant in the storage medium.
 19. A cooling systemfor a vehicle according to claim 15, wherein a compressor of the airconditioner comprises an electric compressor for a variable coolingpower, and the cooling power is increased, as heat-exchange between thecoolant and the refrigerant is carried out.
 20. A cooling system for avehicle according to claim 15, wherein the unit is a fuel cell.
 21. Acooling method for a unit carried on a vehicle, comprising: connecting acoolant circuit for circulating coolant to cool the unit, and arefrigerant circuit for circulating a refrigerant for an air conditionerof the vehicle to a heat exchanger including a storage medium, a coolantregion connected to the coolant circuit, and first and secondrefrigerant regions connected to the refrigerant circuit, the heatexchanger being capable of performing a first heat-exchange betweencoolant of the coolant region and refrigerant of the first refrigerantregion, a second heat-exchange between the storage medium andrefrigerant of the second refrigerant region, and a third heat-exchangebetween the coolant and the storage medium; carrying out the firstheat-exchange by using a coolant line switching valve provided in thecoolant circuit to cause the coolant to flow into the coolant region ofthe heat exchanger, and by using a refrigerant line switching valveprovided in the refrigerant circuit to cause the refrigerant to flowinto the first refrigerant region of the heat exchanger; carrying outthe second heat-exchange by using the coolant line switching valve toshut off the flowing of the coolant into the heat exchanger, and byusing the refrigerant line switching valve to cause the refrigerant toflow into the second refrigerant region of the heat exchanger; carryingout the third heat-exchange by using the refrigerant line switchingvalve to shut off the flowing of the refrigerant into the heatexchanger, and by using the coolant line switching valve to cause thecoolant to flow into the coolant region of the heat exchanger; andstopping the first, second and third heat-exchanges by using therefrigerant line switching valve to shut off the flowing of therefrigerant into the heat exchanger, and by using the coolant lineswitching valve to shut off the flowing of the coolant into the heatexchanger.
 22. A cooling method according to claim 21, furthercomprising: calculating a temperature increase rate of the coolant;calculating an output increase rate of the unit, wherein the thirdheat-exchange is carried out when the temperature increase rate of thecoolant and the output increase rate of the unit are respectively equalto or higher than setting values.
 23. A cooling method according toclaim 22, wherein the first heat-exchange is carried out, as atemperature of the coolant is equal to or higher than a firstpredetermined value.
 24. A cooling method according to claim 23, whereinthe third heat-exchange is carried out in dependence to the temperatureincrease rate of the coolant and the output increase rate of the unit,and the first heat-exchange is carried out in dependence to atemperature of the storage medium, as the temperature of the coolant islower than the first predetermined value and equal to or higher than asecond predetermined value lower than the first predetermined value. 25.A cooling method according to claim 24, wherein the second heat-exchangeis carried out, as the temperature of the coolant is lower than thesecond predetermined value, the temperature of the storage medium isequal to or higher than a stipulated value, and a temperature in a carroom is in a range of a given temperature from a set temperature.
 26. Acooling method according to claim 21, wherein the unit is a fuel cell.27. A method for cooling a unit carried on a vehicle, comprising:connecting a coolant circuit for circulating coolant to cool the unitand a refrigerant circuit for circulating a refrigerant for an airconditioner of the vehicle to a heat exchanger including a storagemedium, first and second coolant regions connected to the coolantcircuit, and a refrigerant region connected to the refrigerant circuit,the heat exchanger being capable of performing a first heat-exchangebetween coolant of the first coolant region and refrigerant of therefrigerant region, a second heat-exchange between the storage mediumand the refrigerant of the refrigerant region, and a third heat-exchangebetween coolant of the second coolant region and the storage medium;carrying out the first heat-exchange by using a coolant line switchingvalve provided in the coolant circuit to cause the coolant to flow intothe first coolant region of the heat exchanger, and by using arefrigerant line switching valve provided in the refrigerant circuit tocause the refrigerant to flow into the refrigerant region of the heatexchanger; carrying out the second heat-exchange by using the coolantline switching valve to shut off the flowing of the coolant into theheat exchanger, and by using the refrigerant line switching valve tocause the refrigerant to flow into the refrigerant region of the heatexchanger; carrying out the third heat-exchange by using the refrigerantline switching valve to shut off the flowing of the refrigerant into theheat exchanger, and by using the coolant line switching valve to causethe coolant to flow into the second coolant region of the heatexchanger; stopping the first, second and third heat-exchanges by usingthe refrigerant line switching valve to shut off the flowing of therefrigerant into the heat exchanger, and by using the coolant lineswitching valve to shut off the flowing of the coolant into the heatexchanger; and carrying out the first and second heat-exchanges by usingthe coolant line switching valve provided in the coolant circuit tocause the coolant to flow into the second coolant region of the heatexchanger, and by using the refrigerant line switching valve provided inthe refrigerant circuit to cause the refrigerant to flow into therefrigerant region of the heat exchanger.
 28. A cooling method accordingto claim 27, wherein the unit is a fuel cell.
 29. A cooling system for avehicle comprising: a coolant circuit for circulating coolant to cool aunit carried on the vehicle; a refrigerant circuit for circulatingrefrigerant for an air conditioner of the vehicle; and a heat exchangerconnected to the coolant and refrigerant circuits, provided with astorage medium including a substance adapted to be cooled by therefrigerant and store thermal energy resulting from cooling of thesubstance by the refrigerant, the heat exchanger being adapted to carryout heat-exchanges between the coolant and the storage medium cooled bythe refrigerant, and between the coolant and the refrigerant.
 30. Acooling system for a vehicle according to claim 29, wherein the unit isa fuel cell.
 31. A vehicle, comprising: a cooling system according toclaim
 30. 32. A vehicle, comprising: a cooling system according to claim29.